Methionine aminopeptidase 1D, also known as MAP1D, is a member of the peptidase M24A family. N-terminal methionine removal is an important cellular process required for proper biological activity, subcellular localization, and eventual degradation of many proteins. The enzymes that catalyze this reaction are called Methionine aminopeptidases (MAPs). MAP1D is overexpressed in colon cancer cell lines and colon tumors as compared to normal tissues (at protein level). Downregulation of MAP1D expression by shRNA in HCT-116 colon carcinoma cells reduces anchorage-independant growth in soft agar. MAP1D binds two cobalt ions per subunit. The true nature of the physiological cofactor is under debate. MAP1D is also active with zinc, manganese or divalent ions. MAP1D removes the amino-terminal methionine from nascent proteins. It may also play an important role in colon tumorigenesis.